Dyeing of organic derivative of cellulose textile material involving the steps of impregnating it with a free leuco vat-dyestuff, oxidation, and alkaline reduction of the oxidized dyestuff



Patented June 3, 1952 UNITED STATES DYEING OF ORGANIC DERIVATIVE F CEL- LULOSE TEXTILE MATERIAL INVOLVING THE STEPS OF IMPREGNATING IT WITH A FREE LEUCO VAT-DYESTUFF, OXIDA- TION, AND ALKALINE REDUCTION OF THE OXIDIZED DYESTUFF William T. Haggerty, Jr., and George C. Ward,

Cumberland, Md., assignors to Celanese Corporation of America, New York, N. Y., a corporation of Delaware No Drawing. Application February 16, 1950,

, Serial No. 144,584

2 Claims.

This invention relates to the dyeing of cellulose acetate or other organic acid ester, of cellulose textile materials and relates more particularly to an improved process for the dyeing of said textile materials with vat dyestuffs in shades fast to light, washing and atmospheric fading.

An object of this invention is the provision of an improved process for the application of vat dyestuffs in the dyeing of textile materials having a basis of cellulose acetate or other organic acid ester of cellulose.

Another object of this invention is to provide an improved process for dyeing cellulose acetate or other organic acid ester of cellulose material with vat dyestuffs whereby the saponification of said organic acid ester of cellulose material is greatly minimized,

A further object of this invention is to provide an improved process for dyeing cellulose acetate or other organic acid ester of cellulose textile materials with vat dyestuffs in level, well penetrated shades which are fast to washing, to light and to atmospheric fading, and which are substantially free from crocking or other undesirable characteristics.

Other objects of this invention will appear from the following detailed description.

The application of vat dyestuffs for the coloration of cellulosic materials yields excellent results due to the resistance of vat dyes to the various agencies to which textile materials are commonly subjected in service. The application of vat dyestuffs to cellulose acetate or other organic acid ester of cellulose textile materials has :not always been entirely satisfactory since the use of strong bases such as sodium hydroxide and strong reducing agents such as sodium hydrosulfite in sufiicient amounts to solubilize the vat dyestuffs and effect sufficient penetration has been found to cause an excessive degree of saponification 0n the cellulose acetate material. Due to the excessive saponification whereby regenerated cellulose is formed the dyed textile materials thus obtained are found to be uncommercial due to an excessive loss in weight which yields a sleezy fabric. These undesirable eifects have been obviated to some extent in the case of cellulose acetate or other organic acid ester of cellulose textile materials of relatively light construction by the use of the so-called acid vats. The vat acid process comprises reducing a vat dyestuif with the aid of sodium hydroxide and sodium hydrosulfite whereby the sodium salt of the leuco vat dyestuflf is formed, followed by the addition of a suitable acid to the vatted dyestuif so that the free leuco compound of the vat dyestufi is formed. The resulting dyeb-ath may then be padded on to the cellulose acetate textile material and the free leuco vat dyestuff thus applied then oxidized back to the colored form with the aid of a suitable oxidizing agent. The addition of a dispersing agent to the free leuco vat dyebath has also been found to be valuable to effect increased penetration. In the case of cellulose acetate fabrics of a relatively heavy construction, such as those which are satisfactory 'for use as suitings, draperies and the like, this process does not yield the same valuable results. Due tothe heavy construction of said fabrics, penetration is not always uniform nor is reduction complete where the amount of alkali and hydrosulfite must be limited to avoid excessive saponification during the period for which the vatted dyestuff is permitted to remain on the fabric to achieve as thorough a penetration as possible.

We have now found that cellulose acetate or other organic acid ester of cellulose textile materials of a relatively heavy construction may be dyed rapidly and satisfactorily in a continuous fashion with vat dyestuffs in well penetrated, level shades without excessive saponification thereof. In accordance with the process of our invention, these valuable results are obtained by employing a pad-dyeing procedure whereby the cellulose acetate or other organic acid ester of cellulose textile material to be dyed is padded with an aqueous dispersion of a free vat dyestuff obtained by employing the vat acid procedure, the fabric then dried, repadded with an aqueous alkaline solution of a sulfoxylate formaldehyde reducing agent for said vat dyestuff containing an alkali metal carbonate, steamed when wet to effect a complete and thorough penetration and distribution of the dyestuff in the fabric, and then oxidized back to the final color employing a suitable aqueous oxidizing bath. The dyed textile material thus obtained, after oxidation is completed, is then soaped, rinsed and finished in the usual manner. The dyed cellulose acetate or other organic acid ester of cellulose textile materials thus obtained not only exhibit excellent resistance to washing; to light and to atmospheric fading, but are substantially free from crocking and from the substantial loss in weight usually observed when vat dyestuffs are applied to cellulose acetate or other organic acid ester of cellulose textile materials. Thus, we have found that in the case of cellulose acetate textile materials having an initial acetyl value of 53 to 54%, calculated as acetic 3 acid, our novel dyeing process yields dyed textile materials of an acetyl value of at least 50%. This limited degree of saponification which takes place is insufiicient to cause the dyed fabric to undergo a loss in weight sufi'icient to impart a sleezy hand thereto.

Any suitable vat dyestufi may be employed in accordance with our novel dyeing process. Examples of suitable dyestuffs are:

Indanthrene Red FBBA Dbl. Pst.

Indanthrene Blue CLN Pst.

Indanthrene Yellow 3G Pst.

Indanthrene Olive TA Pst.

Indanthrene Red Brown 5RF Pst.

Ponsol Jade Green Dbl. Pst. (C. I. 1101) Indanthrene Olive RAP Pst. (C. I. 1150) Indanthrene Dark Blue BOF Pst. (C. I. 1099) Indanthrene Blue IBCSN Dbl. Pst. (C. I. 1114) Indanthrene Violet FFBNA Pst.

The aqueous dyestufi' dispersion is applied, as mentioned, by padding operations employing a suitable padding mangle provided with one or more nips so that the desired degree of penetration may be achieved.

The vat dyestuff dispersion thus applied is prepared by mixing a paste of the finely divided vat dyestufi employed with caustic soda, sodium hydrosulfite and a suitable dispersing agent such as sodiumnaphthalene sulfonate, for example. The vat dyestuff is thus reduced and converted to the sodium salt of the leuco vat dyestufi. When the dyestuif has been vatted, aqueous acetic acid is added thereto to neutralize the alkali metal salt of the leuco vat dyestufi and convert the same to the corresponding free leuco vat dyestuff. The resulting dispersion of free vat dyestuif is padded onto the fabric. The concentration of dyestuff in the dyebath will vary depending upon the depth of shade desired in the dyed cellulose acetate material. The dyebath is usually made up to contain from 0.1 to 5% by weight of dyestufi on the weight of the bath.

In forming the free leuco vat dyestufi, one part by weight of the dyestuif paste is mixed with from 0.2 to 1 part by weight of sodium hydroxide, 0.2 to 1 part by weight of sodium hydrosulfite on the weight of the dyestuff and from 0.2 to 1 part by weight of the dispersing agent em-.- ployed is added thereto. A sufl'icient amount of acid, for example acetic acid, is then added to the resulting mixture so as to neutralize the alkali present and to form the free leuco vat dyestuif. The amount of water added with the acetic acid will vary depending upon the concentration of dyestufi desired in the dyebath. The dyebath is usually maintained at a temperature of 40 to 65 C. during the padding operation. After the cellulose acetate textile material has been padded with the dispersion of the free leuco vat dyestuif prepared as described above,

it is preferably dried before being padded with the aqueous sulfoxylate formaldehyde and alkali metal carbonate solution. Drying may be conveniently efiected by passing the padded material into a tower through heated air is circulated. Heated drums or cans or a tenter frame .may also be employed for drying the padded cellulose acetate material.

Since the vat acid dyestufi is easily oxidized, drying in air converts it back to the oxidized state. However, the dyestufi is not fixed to the textile material and a re-reduction is necessary to obtain the necessary fixation.

The dried cellulose acetate material with the vat dyestuif present thereon is then padded with an aqueous solution of a sulfoxylate formaldehyde reducing agent, which solution is rendered alkaline by the addition of an alkali metal carbonate such as sodium carbonate or potassium carbonate thereto. The alkali metal carbonate is a mild alkaline agent and serves to aid in the solubilization and complete reduction of the free leuco vat dyestufi. The sulfoxylate formaldehyde which we have found to yield the most desirable results in achieving satisfactory dyeings is sodium sulfoxylate formaldehyde. The aqueous solution employed in padding the dried cellulose acetate material carrying the free leuco vat dyestuif may contain from 1.5 to 12% by weight on the solution of the sulfoxylate formaldehyde and from 1.5 to 12% by weight on the solution of the alkali metal carbonate. A thickening'agent such as sodium alginate, gum tragacanth, karays or gum arabic may also be employed in forming the second padding solution in an amount of from 0.2 to 5% on the weight thereof.

Complete penetration, fixation and reduction of the vat dyestuif present on the cellulose acetate material is then eifected by steaming the vantageously, the steaming is carried out for about 5 minutes at a steam pressure of about 5 lbs. gauge.

To oxidize the free leuco vat dyestuff back to the colored form, the cellulose acetate material is withdrawn from the ager and then entered into an aqueous oxidizing bath containing from 0.2 to 1% by weight of sodium perborate, or other suitable oxidizing agent such as sodium dichromate or the like. Complete oxidation is usually attained by maintaining the textile material in the oxidizing bath for to 10 minutes with the oxidizing bath at a temperature of 40 to 70 C. The oxidation treatment converts the free leuco vat dyestuif to the final desired shade and the dyed cellulose acetate material is then soaped, rinsed, dried and finished.

The dyed cellulose acetate textile materials thus obtained are not only fast to light, to atmospheric fading and substantially free from crocking, but the dyed textile materials also ex- Example A cellulose acetate fabric of a sharkskin weave consisting of 52 ends per inch of cellulose acetate yarns of 300 denier in the warp and 39 picks per inch of 600 denier in the filling is padded with the following dispersion:

. Parts by weight Indanthrene Red FBBA Dbl. Pst. 10

Sodium hydroxide 5 Sodium hydrosulfite 5 Sodium naphthalene sulfonate 5 Acetic acid (56%) 15 Water 460 The dispersion is padded on to the fabric at a temperature of 50 C., the nip of the padding mangle being so adjusted as to place 50% on the weight of the fabric of the dispersion thereon. The fabric is then dried in a hot flue and repadded with the following composition:

Parts by weight Sodium sulfoxylate formaldehyde 60 Sodium carbonate 60 Sodium alginate 3 Water 377 This second solution is padded on the fabric at a temperature of 40 C. The wet fabric coming from the pad is then immediately steamed for 5 minutes with steam at a pressure of 5 lbs. gauge and, after steaming is completed, the fabric is rinsed, oxidized in a 0.5% by weight aqueous solution of sodium perborate at 50 C. for 2 minutes and then soaped, rinsed and dried. The fabric is dyed a bright red shade and is found to exhibit excellent fastness to light, washing and atmospheric fading and to be substantially free from crocking. The original cellulose acetate fabric employed was composed of yarns having an acetyl value of 54%, calculated as acetic acid. After dyeing, the cellulose acetate yarns are found to have an acetyl value of 50%.

While our invention has been more particularly described in connection with the dyeing of cellulose acetate textile materials, this novel dyeing process is equally valuable for the dyeing of other organic acid ester of cellulose textile materials. Examples of other organic acid ester of cellulose textile materials are cellulose propionate, cellulose butyrate and mixed esters of cellulose such as cellulose aceto-propionate and cellulose acetobutyrate. Our novel dyeing process may also be employed in the dyeing of cellulose ether materials such as ethyl cellulose and benzyl cellulose. While cellulose ethers are not subject to undesirable saponification during vat dyeing operations, the fastness of the colors obtained on said cellulose ether materials may be substantially improved by employing our novel process in the coloration of said materials.

Our process is applicable not only to the dyeing of fabrics, but other textile materials such as yarns, filaments or staple fiber in the form of a top or roving may also be dyed in unusually fast colors employing our novel process.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the coloration of textile materials which comprises mechanically impregnating an organic derivative of cellulose textile material with an aqueous dispersion of a free leuco' vat dyestuif, drying the impregnated textile material in air whereby the dyestufi is oxidized, impregnating the dried textile material with an aqueous impregnated textile material in air whereby the dyestuif is oxidized, impregnating the dried textile material with an aqueous solution containing 1.5 to 12% by Weight of sodium sulfoxylate formaldehyde and 1.5 to 12% by weight of sodium carbonate, steaming the wet textile material again to reduce and fix the free leuco vat dyestuff on the textile material, and then oxidizing the vat dyestufi to the final colored form in an aqueous oxidizing bath.

WILLIAM T. HAGGERTY, JR.

GEORGE O. WARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,415,379 Vieira Feb. 4, 1947 2,424,857 Scull July 29, 1947 OTHER REFERENCES American Dyes, Reporter for Dec. 29, 1947, pages P775, P776, P777, P784 (article by Hennessey) American Dye, Reporter for Feb. 26, 1945, pages P99, P100, P101 (article by Stribling) 

1. PROCESS FOR THE COLORATION OF TEXTILE MATERIALS WHICH COMPRISES MECHANICALLY IMPREGNATING AN ORGANIC DERIVATIVE OF CELLULOSE TEXTILE MATERIAL WITH AN AQUEOUS DISPERSION OF A FREE LEUCO VAT DYESTUFF, DRYING THE IMPREGNATED TEXTILE MATERIAL IN AIR WHEREBY THE DYESTUFF IS OXIDIZED, IMPREGNATING THE DRIED TEXTILE MATERIAL WITH AN AQUEOUS SOLUTION CONTAINING 1.5 TO 12% BY WEIGHT OF SODIUM SULFOXYLATE FORMALDEHYDE AND 1.5 TO 12% BY WEIGHT OF SODIUM CARBONATE, STEAMING THE WET TEXTILE MATERIAL AGAIN TO REDUCE AND FIX THE FREE LEUCO VAT DYESTUFF ON THE TEXTILE MATERIAL, AND THEN OXIDIZING THE VAT DYESTUFF TO THE FINAL COLORED FORM IN AN AQUEOUS OXIDIZING BATH. 